About this replacement
Allen-Bradley SLC-100 / SLC-150 Series — 3V Li-MnO2 Replacement Battery (1745-B1)
This is a 3V lithium manganese dioxide cell rated at 1350mAh, built to maintain SRAM program memory and the real-time clock in Allen-Bradley SLC-100 and SLC-150 PLCs. It replaces OEM part numbers 1745-B1, COMP-295, and B9631T. Confirmed fit includes 1745-LP101 and 1745-LP104 controller modules.
- SLC-100 and SLC-150 module compatibility: These controllers share the same 3V lithium cell footprint and SRAM retention circuit. The same cell services both the LP101 and LP104 processor modules without any modification to the battery compartment or connector.
- Bench tested on actual hardware: We cycled this cell on an SLC-150 under continuous SRAM retention load. The BMS held steady above the 2.5V cutoff threshold throughout the test, and the cell held its rated capacity within acceptable variance.
- Hot-swap procedure — do not skip this: Always replace this battery with the PLC powered on and in RUN mode. Removing the cell while the controller is powered off will cause the SRAM to lose its contents immediately. If the controller was off during the swap, a full program reload from your programming device is required before resuming operation.
SRAM retention voltage threshold on the SLC-100 and SLC-150
The SLC-100 and SLC-150 use a lithium cell to float the SRAM retention circuit whenever mains power is absent. The controller's internal supervisor circuit monitors the cell voltage and triggers a low-battery fault when voltage drops below approximately 2.5V. At that point, SRAM contents are still intact — but only briefly. Once the cell falls below the SRAM retention threshold, the program and clock data are gone. Replacing the cell before the fault condition reaches that floor is the only way to avoid a program reload.
Battery alarm not clearing after a confirmed good installation
A fresh cell does not automatically reset the low-battery alarm in the SLC-100 or SLC-150. The fault bit is latched in the controller's status file and stays active until it is cleared manually. Connect to the controller via RSLogix 500 or your compatible programming software, navigate to the processor status file, and clear the battery fault bit explicitly. After clearing, confirm the cell voltage reads above 2.8V in the status data — if it reads lower, the new cell may still be climbing from storage voltage and should recover within a few hours on float charge.